During the manufacturing, printing, processing, or use of a moving web, dirt or other particles may be generated. If such particles adhere to the web, the particles may cause defects in the web resulting in the web being unsuitable for its intended use. For example, with photosensitive web material, dirt on the web may scratch the web's photosensitive layers during manufacture, or the dirt could be exposed during processing to form a visual defect in the printed photographic product.
Therefore, it is desirable to clean the web surface to remove particles from the web thereby reducing or eliminating potential defects in the web. During manufacturing, the cleaning of the web surface is preferably conducted such that the impact on the manufacturing process is minimized, the web is not adversely affected, and no quality defects are introduced to the web.
Systems for removing particles from a web surface are known. For example, air knives and suction cleaning systems. Particle transfer rollers have been suitable to remove particles. Such a particle transfer roller (PTR) typically has an adhesive or tacky surface to which particles from the web surface adhere upon contact with the PTR. As the particles accumulate on the PTR, the PTR becomes contaminated and must be cleaned periodically to restore/renew its effectiveness.
U.S. Pat. Nos. 5,425,813 and 5,337,767, commonly assigned, relate to an apparatus and method of cleaning a moving web, and more particularly, for renewing (i.e., cleaning) a PTR. One PTR is brought into contact with the moving web while another PTR is being cleaned with a renewal roller through wiping contact. The PTRs are not moving as they contact the web. Therefore, if such PTRs were applied to a moving web, scratches or abrasions may occur, particularly for webs moving at a high speed. Further, if a build-up occurs in the absorbent cleaning member, the PTR renewal effectiveness may be decreased.
U.S. Pat. No. 5,275,104 relates to an automatic roll cleaner which provides cleaning through slippage between the cleaning material and the roller. While such an apparatus may be suitable for a particular application, slippage would cause scratches and abrasions in a photosensitive material.
U.S. Pat. No. 5,251,348 relates to a roll cleaning system. A drive motor drives an out-of-service roll while it is being cleaned. A turret is then indexed to bring the cleaned roller in contact with a moving web. The roll is tacky and adhesive, and if the speeds did not match, the roll would grab, disrupt, and even damage the moving web.
U.S. Pat. No. 5,198,243 relates to a roll cleaning apparatus having a cleaning tape for wiping the surface of a roll. While such an apparatus may be suitable for its particular application, such an apparatus would scratch photosensitive web material.
U.S. Pat. No. 4,982,469 and U.S. Pat. No. 4,009,047 relate to apparatus for cleaning a surface of a sheet. While such apparatus may be suitable for their respective application, not controlling the speed of the sheet and the cleaning roller(s) may cause scratches or abrasions in the sheet, particularly photosensitive material.
Accordingly, a need continues to exist for an apparatus and method for removing contaminants from a moving web. Such an apparatus and method should not introduce defects (e.g., abrasions or scratches) to the moving web. The apparatus and method should provide for renewing the cleaning capability of the contaminant-removing apparatus without disrupting the moving web (e.g., stopping the moving web). Such an apparatus and method should be suitable for webs moving at a high rate of speed and webs which are photosensitive.